Photographer captures puppies underwater in adorable new series

An American animal photographer has captured the adorable faces of puppies learning to swim, some breaking through the surface of the water for the first time.

Seth Casteel worked with over 1,500 puppies to create the underwater series (though not all were photographed), which involved him wearing a wet suit, playing with pet toys and holding his breath for up to 60 seconds.

The heart of the project was to teach puppies to swim safely in pools, so the artist began placing the puppies in the water and showing them where the exit was. The rest they worked out themselves.

Casteel started volunteering to photograph homeless pets to help them find loving families in 2007, and he became an overnight sensation when his first photos of dogs underwater went viral.

In 2012, the pictures were collated in a tome titled Underwater Dogs, which went onto become a New York Times best-seller.

Speaking about the series, Casteel said, "Puppies lift our spirits. They don't care who you are, what you've been doing, where you're going, they just want to love you and they just want to be your friend. And I think that's always going to make us feel good."

"The goal [of the book] was to feature some Amazing Rescue Puppy Ambassadors to remind people that adoption is a wonderful option!" Casteel writes on his website. "There are so many AWESOME pets that need loving families and I hope you'll consider bringing a shelter pet into your life."

Take a look at more puppies and their adorable underwater expressions below.